This invention relates to three-dimensional displays; more specifically, this invention relates to such displays that use electro-optic media to modulate the passage of light along a waveguide.
Most displays (using “displays” in a broad sense to include fixed images on paper or similar materials) are two-dimensional, and use of such two-dimensional images to construct real three-dimensional objects can lead to difficulties. For example, many people have trouble envisioning the final appearance of a three-dimensional object from a set of two-dimensional images, and it may be difficult to detect awkward relative placements of objects or awkward sightlines from two-dimensional images. Hence, it is useful to represent three-dimensional objects in such a way that the spatial relationships between the various components of the objects are apparent. Three-dimensional displays are known; for example, three-dimensional displays which include waveguides based on liquid crystal (LCD) technology have been described, for example in U.S. Pat. No. 5,812,186. However, liquid crystalline materials may introduce an angular dependence of light modulation which can limit the performance of such three-dimensional displays, for example, by sacrificing how the object is viewed from certain perspectives.
It is known that modulation of light travelling along optical fibers can be effected by so-called “frustrated internal reflection” where internal reflection at the surface of a waveguide is prevented by bringing a material of relatively high refractive index adjacent a surface of the waveguide; see for example U.S. Pat. No. 5,317,667.
It has now been realized that three-dimensional displays which do not suffer from the known disadvantages of three-dimensional liquid crystal displays can be constructing using electrophoretic and other electro-optic media.